The present invention relates generally to hearing aids, and more particularly, to hearing aids having a sandwich type switch construction with a deformable elastomeric membrane.
Hearing aids require switches which are used for a variety of purposes including on/off control, volume control, trimmer applications such as noise filtration control, and telecoil control such as a telephone receiver mode, etc. Hearing aid switches for both in-the-ear hearing aids and behind-the-ear hearing aids must be miniature to fit within the small space requirements of the hearing aid housings and to maintain the aesthetic qualities of hearing aids.
Conventional wiper switches used in hearing aids include a wiper having a first end electrically and pivotally coupled to circuitry and a second or contact end which is wiped across either a nonconductive surface to open the switch or across a conductive surface to close the switch. The wiper switch is constructed to wipe across a variable resistance path if the wiper switch is to used for volume control or noise filtration. However, wiper switches have several drawbacks. Since the voltage through hearing aid circuits is low, wiper switches require precise fabrication to ensure electrical contact and to avoid generating electrical noise. Precise fabrication is costly and requires the use of miniature parts which are difficult to handle and which tend to wear out and cause the switch to malfunction.
A push button switch is disclosed in U.S. Pat. No. 4,634,815 to Marquis for turning the hearing aid on and off and for volume control. The switch is activated by rotating the button such that a contact tongue contacts a contact member to close a circuit. To control the volume, the push button is pressed causing a diaphragm to depress and close another circuit. Volume control is either limited to two settings or is changed in proportion to the time period for which contact is maintained.